I'm stuned by this response... you say 'right' to 2(two) opposed things!
as sven points out, it depends on the server + the persistance manager + db
tx isolation support...
however sven, I'm afraid that no App Server implementation on the market
today does check for extra JVM
race conditions/deadlocks... in an app server clustered solution (involving
more than one VM), there's
no locking mechanism that cannot fail when concurrency doesn't ocurr within
the same VM.
There have been numerous posts on the list on that subject, starting at
Ago-2000
It then boiled down to locking widgets that allowed for optimistic,
connectionless, DB-independant row/entity locking.
One of the solutions I proposed(along with many other people) is to use BMP
and add a version field to each row/entity
there are, however, tx isolation properties that made this approach not
enough for all purposes(which I won't enumerate right now)
My 2c,
JP
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]
Sent: Jueves, 11 de Enero de 2001 9:50
To: [EMAIL PROTECTED]
Subject: Re: simple Entity Bean object question.
Sandeep Uppal
Wipro Technologies
---------------------------------------
Hi,
I just want to clarify a point regarding an entity bean objects.
If say a customer table indexed on custid is to be exposed as entity
objects. Assume that there is already
a record with custid = "111".
Now when 5 concurrent clients access this same entity bean, will the
scenario be such that:
a. in the ejb server, there will be 5 corresponding ejbObjects for the 5
client respectively.
b. all the 5 ejbObjects will reference the same instance(one) of the entity
bean representing
that record.
If the above is true, and certainly what I believe in.
>Sandeep: right
Then how is
synchronization between
difference ejbObjects making changes to the same entity bean implemented.
>Sandeep: how is the synchronization maintained when two people are
updating the database. Transactions!!!!!!!!
Any comments will be very helpful.
Thanks,
Magesh.
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